<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>结构伪类选择器</title>
    <style>
        div{
           width: 100px;
           height: 100px;
        }
        /* 没有元素 */
        div:empty{
            background: red;
        }
    </style>
</head>
<body>
    <div>
       1111111111111
    </div>
    <div></div>
</body>
</html>